Data Sheet

10.13.2009 PRODUCT SPECIFICATION proprietary to OmniVision Technologies
4-7
4.4.6 average based AEC/AGC
As shown in figure 4-4, the average based AEC/AGC algorithm makes the average value of the luminance converge to
the Stable Operating Region step by step. Outside the Control Zone, the AEC/AGC adjusts exposure time and gain by
big steps to lower luminance quickly. Inside the Control Zone and outside the Stable Operating range, the AEC/AGC
adjusts exposure time and gain by small step to make the luminance level converge to the Stable Operating Region
smoothly. Inside Stable Operating Region, the AEC/AGC does not adjust exposure time and gain anymore.
table 4-6
summarizes the control registers of the average based AEC/AGC.
figure 4-4 average based AEC/AGC
table 4-6 average based AEC/AGC registers
address register name description
0x24 AEW Bit[7:0]: Upper limit of the Stable Operating Region
0x25 AEB Bit[7:0]: Lower limit of the Stable Operating Region
0x26 VPT
Bit[7:4]: High nibble of upper limit of fast mode control zone
The upper limit is {0x26[7:4], 4’h0}
0x26 VPT
Bit[3:0]: High nibble of lower limit of fast mode control zone
The lower limit is {0x26[3:0], 4’h0}
0x0D COM4
Bit[5:4]: Average option (must be same value as 0x0D[7:6])
00: Full window
01: 1/2 window
1x: 1/4 window
0x42 COM17
Bit[5:4]: Average option (must be same value as 0x42[5:4])
00: Full window
01: 1/2 window
1x: 1/4 window
control zone stable operating region
desired convergence
7675_DS_4_4
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